Heretofore, as one type of filter, which filters a liquid that serves as an object to be processed, a bag filter, which utilizes a bag element, is known (see, e.g., Japanese Laid-Open Patent Publication No. 2003-154213 and Japanese Laid-Open Patent Publication No. 2008-093644). FIG. 1 is a vertical cross-sectional view showing a conventional example of a bag filter 100. As shown in FIG. 1, the bag filter 100 comprises a container 102 and a plurality of legs 105 supporting the container 102.
The container 102 includes a casing 103, the upper end of which is open, and which forms a main body section of the container 102, and a dome-shaped cover 104 that closes the upper end of the casing 103. The cover 104 closes and seals the upper end of the casing 103 in a condition where a gasket (not shown) is disposed between the casing 103 and the cover 104. The cover 104 and the casing 103 are fixed together by wrapping a ring-shaped tightening band 107 therearound and tightening the same.
The casing 103 includes an inlet port 106 disposed on an upper side of an outer peripheral surface thereof, through which a liquid to be processed (filtered) is introduced, and a discharge port 108 disposed on a lower side of the outer peripheral surface thereof, through which the filtered liquid is discharged. On a lower portion of the container 102, a liquid removal port 110 is further provided for discharging liquid that has collected in the container 102, for example when a maintenance operation is carried out. Respective tubes (not shown) are connected to the inlet port 106, the discharge port 108 and the liquid removal port 110. A basket 112 is installed inside the container 102. The basket 112 is a cylindrical shaped container having an open upper portion. A bag-like filter element 114 (see FIG. 2A) is accommodated inside the basket 112.
FIG. 2A is a perspective view of the basket 112 and the filter element 114. As shown in FIG. 2A, an inverted U-shaped pressing member 116 is connected to an upper edge of the basket 112. In a state where the casing 103 is closed by the cover 104, the basket 112 receives a downwardly directed pressing force from the pressing member 116 due to the cover 104 pressing down on the pressing member 116.
FIG. 2B is an enlarged view of a portion A shown in FIG. 1. As shown in FIG. 2B, the basket 112 includes an upper tubular portion 118 forming the upper part of the basket 112, and a cylindrical shaped main body section 120 formed with a reduced diameter, which is smaller than that of the upper tubular portion 118, and in which a major part of the filter element 114 is accommodated. The main body section 120 is formed from a metal mesh or a perforated (porous) metal plate.
An annular gasket receiving member 122 is placed in intimate contact with the inner circumferential surface of the casing 103. The basket 112 is supported by the gasket receiving member 122 through a ring-shaped flat gasket 124, which is mounted on the gasket receiving member 122. As described above, because the basket 112 receives a downwardly directed force from the pressing member 116, due to the flat gasket 124 being pressed by such a pressing force, a seal is formed between the basket 112 and the gasket receiving member 122. Such a seal has the object of preventing leakage of unfiltered liquid toward the side of the discharge port 108.